Board Thread:General Discussion/@comment-26869340-20170217143005/@comment-31433193-20170217144309

The nature of a Pokémon affects its performance during battle. For example, a Modest Charizard has its Sp. Atk boosted, but its Atk dropped. If it uses Flamethrower, it'll do slightly better than it usually does; if it uses Fire Fang, it will not deal as much as usual as its nature affected it.

Non-neutral natures have a 1.1x boost for Green-highlighted stat, and a 0.9x drop for Yellow-highlighted stat.

Bashful is an example for a neutral nature, that means no stats are additionally altered. However, it is not beneficial because what you are looking for is an additional boost in attacking powers.